Preparation of acrylic acid



United States Patent 3,340,296 PREPARATION OF ACRYLIC ACID Edwin MarvinSmolin, Springdale, Conn., assignor to American Cyanamid Company,Stamford, Conn., a corporation of Maine No Drawing. Continuation ofapplication Ser. No.

163,037, Dec. 29, 1961. This application June 6,

1966, Ser. No. 555,619

3 Claims. (Cl. 260-533) This is a continuation of application Ser. No.163,037, filed Dec. .29, 1961, and now abandoned.

This invention relates to a novel method for preparing acrylic acid.More particularly, the invention relates to an improvement in nickelsalt-copper salt-catalyzed liquidphase reactions at elevatedtemperatures and pressures of equivalent amounts of acetylene, carbonmonoxide and Water. Still more specifically, it is concerned with animprovement in carrying out such a reaction whereby the time requiredfor its completion is substantially reduced.

It is known that equivalent quantities of acetylene, carbon monoxide andwater may be reacted in the liquid phase to give acrylic acid providingelevated temperatures, elevated pressures and a nickel salt-copper saltcatalyst combination are used. However, this process is not entirelysatisfactory and leaves much to be desired. For example, in highpressure liquid-phase reactions as previously practiced, the time forinitiating the reaction is unduly long. In the continuous synthesis ofacrylic acid, there is usually a considerable lapse of time, forexample, from five to fifteen hours, before the reaction proc eeds at asatisfactory rate, all materials being fed continuously andproportionally. This long induction period requires long residence timesfor the completion of the high pressure liquid-phase reaction processand not infrequently polymerization and other reactions of acrylic acidoccur with attendant loss of yield.

Since acrylic acid finds extensive use in the manufacture of syntheticresins for application in surface coatings, adhesives, etc., as well asin the formation of acrylic acid esters capable of similar end uses, animproved procedure for its manufacture has long been desired.

While numerous modifications in the general process for the nickelsalt-copper salt-catalyzed liquid-phase reaction at elevatedtemperatures and pressures of acetylene, carbon monoxide and water havebeen made, nevertheless, the problem of shortening or lessening theinduction period and, of course, the overall reaction time has not tothe present been solved.

According to the present invention, however, the difficulties heretoforeencountered have been substantially eliminated while effecting reactionwithin a relatively short period of time.

Pursuant to the instant discovery, it has been found that the inductionperiod and the overall reaction time may be substantially reduced in asurprisingly straightforward manner. This is accomplished by firstintroducing into a reaction vessel which is charged with reactionliquid, i.e., water, solvent and a nickel salt-copper salt catalystcombination, a small quantity of acetylene or acetylene-containing gas.A reaction, which is not completely understood, would appear to takeplace among the water, catalyst and acetylene. This is usually evidencedby a lowering of pressure within the reaction vessel of from about 50 toabout 150 pounds per square inch gauge from the original total elevatedpressure within the vessel producedby the introduction of acetylene. Thedesired reaction, i.e., production of acrylic acid, is commenced bythereafter adding to the vessel approximately equivalent quantities ofacetylene and carbon monoxide. Pretreatment of the reaction liquid maythus be accomplished with a substantially purified acetylene feed orwith an acetylene stream which is diluted with such gases as those whichare inert under the conditions of reaction including, for example,nitrogen, methane, ethane and the like.

While the use of excess acetylene during the entire course of thereaction has been previously known to reduce the overall reaction time,in contrast thereto it has been discovered that pretreatment of thereaction liquid with a small quantity of acetylene is surprisinglyadvantageous in reducing the induction period. By this procedure, thehazards involved in maintaining an excess of acetylene within thereaction vessel during the entire course of the reaction may be avoided.Yet, at the same time, the overall reaction time is substantiallyreduced and the necessity for supplying excess acetylene to the systemwhich must subsequently be recovered and recycled is avoided.

It is an advantage of the present invention that the pretreatment of thereaction liquid; that is, water, solvent and nickel salt-copper saltcatalyst combination, with acetylene or acetylene-containing gas,permits the reaction to take place at a given rate more smoothly andeasily following the induction period which is reduced from a period ofhours to minutes because of such procedure.

In general, the reaction may be conducted in the presence of a widevariety of nickel salt-copper salt catalyst combinations. Thus, forexample, a nickel halide such as nickel chloride, nickel bromide ornickel iodine in combination with a copper halide such as copperchloride,

copper bromide or copper iodide is satisfactory. Particularlyadvantageous, however, is the use of a combination of catalystscomprising a nickel or copper hydrocarbon sulfonate together with anickel or copper halide. The use of such combination of catalysts ofthis type is described and claimed in copending application, Ser. No.776,403, filed Nov. 26, 1958, now United States Patent No. 3,025,- 322.Illustrative metal hydrocarbon sulfonate catalysts suitable for use inthe process of the present invention are nickel methane sulfonate,copper methane sulfonate, nickel ethane sulfonate, copper ethanesulfonate, nickel hexane sulfonate, copper hexane sulfonate, nickelbenzene sulfonate, copper benzene sulfonate, nickel isopropylbenzenesulfonate, copper isopropylbenzene sulfonate, nickel para-toluenesulfonate, copper para-toluene sulfonate, nickel decylbenzene sulfonate,copper decylbenzene sulfonate, nickel 2-naphthalene sulfonate, copper 2-naphthalene sulfonate, nickel dodecylbenzene sulfonate, copperdodecylbenzene sulfonate, nickel bis(2,2-ditolylbutane)sulfonate, copperbis(2,2-ditolylbutane)sulfonate, nickelbis(2,2-diphenylbutane)sulfonate, copper bis(2,2- diphenylbutanesulfonate, nickel bis 1,1-dixylylethane) sulfonate, copperbis(1,l-dixylylethane)sulfonate, and the like and mixtures thereof.

In conjunction with such metal hydrocarbon sulfonate catalysts, nickelor copper halides such as nickel chloride, copper chloride, nickelbromide, copper bromide, nickel iodide, copper iodide and mixturesthereof may be used.

Best results are usually achieved when the hydrocarbon sulfonate and thehalide have different metal cations. For instance, when nickelpara-toluene sulfonate is the metal sulfonate, a copper halide, such ascopper bromide, is used. Similarly, when copper para-toluene sulfonateis the metal sulfonate, a nickel halide, such as nickel bromide, isused.

Very desirable results are obtained when a nickel-containing catalyst ispresent in a molar excess with respect to the copper catalyst, usuallyin the mole ratio range of 2:1 to 4:1. However, the range of 1:1 to 6:1is also suitable.

Generally, the catalysts are present in sufiicient quantity to providefrom 0.1 to 8.0 percent by weight of nickel salt, preferably 0.2 to 5.0percent by weight, basis the total Weight of the non-gaseous mixture.Likewise, a sufii- In carrying out the reaction of acetylene, carbonmonoxide and water in the presence of a catalyst combination ascontemplated herein, it is very advantageous to use an excess by volumeof an inert oxygen-containing organic solvent which is inert to thereactants under the reaction conditions and miscible with water. Inother words, the

solvents are not irreversibly changed by the presence of water and arenot able to react with acetylene 01- carbon monoxide. The solvents,therefore, should not contain free hydroxy, mercapto, or carboxy groups,olefinic or acetylenic linkages, or primary or secondary amino groups.The

boiling points of the solvents are preferably below that of acrylicacid.

Preferred solvents are cyclic ethers, such as tetrahydrofuran, dioxane,and saturated aliphatic ketones, such as acetone, methyl ethyl ketoneand diethyl ketone.

While a slight excess of the solvent with respect to the water employedis suitable, for example, 60 parts by volume of solvent for 40 parts byvolume of water, much 'greater excesses of the liquid organic solventare preferred.

ever, that the partial pressure of acetylene in the gaseous phase doesnot exceed about 450 pounds per square inch gauge.

The process of the instant invention may be conducted in a batch,semi-continuous and continuous manner.

The water component utilized in the instant discovery may be present inan equivalent amount, basis the acetylene and carbon monoxide reactants.More commonly, however, these gaseous components are used in excess overthe water. An excess of acetylene and/ or carbon monoxide over water of10 to 20 molar percent or more, for example, is often desirable, but notessential.

In order to facilitate an understanding of the present invention,thefollowing illustrative examples are given:'

Example 1 A 12% solution of water in acetone containing a nickelsalt-copper salt catalyst combination is charged to a pressure reactionvessel in an amount calculated to give the desired conversion of waterto acrylic acid while, at the same time, an acetylene feed stream isalso passed thereinto. When the reactor is fully charged with liquid andgas and brought to temperature, no further liquid feed is introduced. Atrickle of acetylene gas is maintained for the purpose of agitation.Within 20 to 30 minutes, an induction period appears to terminate asevidenced by a pressure drop of from about 700 p.s.i.g. to about 600p.s.i.g. Thereupon, an acetylene and carbon monoxide mixture is admittedinto the vessel together with additional reaction liquid. Reactionsolution and suflicient unreacted gases are purged so as to maintain thetotal pressure at about 650 to 750 p.s.i.g.

The following table contains a summary of experimental results obtainedwhen the procedure outlined above was followed and demonstrates theeffect on percent conversion to acrylic acid which is produced when thereaction liquid medium is pretreated with acetylene prior to thereaction of water, acetylene and carbon monoxide.

TABLE I.EFFEOT ON CONVERSION OF PRETREATMENT WITH ACETYLENE be conductedat temperatures as low as 150 C. and as high as 220 C. Preferably,reaction temperatures in the range of about 160 C. to about 205 C. areemployed. Pretreatment of the reaction liquid with acetylene oracetylene-containing gas may be accomplished at temperatures from about20 C. to about 150 C. On the other hand, total pressures as low as 300pounds per square inch gauge and as high as about 900 pounds per squareinch gauge are suitable, yet total pressures in the range of'about 450pounds per square inch gauge to about 840 pounds per square inch gaugeare preferred. Much higher total pressures may also be employed, forexample, up to several decylbenzene sult'onate and 0.05- 0.2% copperdecylbenzene sultonate or (popper bromide.

Example 2 In order to further substantiate the results appearing inTable I and to demonstrate the utility of the process of the presentinvention for batch as well as for continuous reactions, a number ofruns were carried out in batch .autoclaves. In this procedure, asuitable pressure vessel is charged with 12% water in acetone plus 0.2%NiBr -3H O, 0.5% CuBr and 0.1% hydroquinone. In Runs BA and BB only, asmall amount of acetylene is then introduced into the vessel whosecontents are maintained at 20 to 2 5? C.

thousand pounds per square inch gauge provided, how- Thereafter, thevesselis heated to the desired reaction temperature and an equimolarmixture of carbon monoxide and acetylene is then admitted into thevessel. Pressure drop taking place within the vessel is then observed.Subsequently, the vessel is cooled to ambient temperature (20 to 25 C.)and the solution produced is removed therefrom.

The results of these runs are summarized in the following table wherethe induction time represents the number of minutes for a100-pound-per-square-inch gauge pressure drop to occur.

From these results, it will be readily observed that pretreatment of thereaction medium is notably efiective in reducing the period forinduction. As a consequence, the overall time for the synthesis ofacrylic acid is markedly lessened.

* Twice the amount of catalyst employed.

While the present invention has been described in detail as to specificembodiments thereof, it is not intended that these details constituteundue limitations upon the scope of the invention, excepting, of course,insofar as these limitations appear in the appended claims.

I claim:

1. In a process for producing acrylic acid by reacting in a reactionmedium approximately equivalent quantities of acetylene and carbonmonoxide at a sufficiently elevated temperature and pressure to formacrylic acid, the improvement comprising a preliminary step of firstadding acetylene to said reaction medium, said adding being in an amountsufficient 1) for a reaction to take place and (2) to thereby reduceinduction period and over-all reaction time, said reaction mediumcomprising (a) a nickel halide-copper halide catalyst combination, (b)water, and (c) an organic, Water-miscible inert solvent.

2. A process according to claim 1 having said acetylene and said carbonmonoxide in a relative mole ratio of from about 2:1 to about 1:2,including reacting sai d first added acetylene at from about 20 C. up toabout 150 C., said elevated temperature ranging from 160 C. up to about205 C., said elevated pressure ranging from about 450 pounds up to about840 pounds including an acetylene partial pressure ranging up to 450pounds, said solvent and said water being in a relative volume ratioranging from about :25 to about :5 of solventzwater, said catalyst beingpresent in an amount ranging from 0.2% to 5% by weight of said nickelhalide, from 0.02 to 5% by weight of said copper halide, and from 0.5 to1% by Weight of non-gaseous reaction mixture.

3. A process according to claim 2, in which said organic, water-miscibleinert solvent is selected from the group consisting of tetrahydrofuran,dioxane, acetone, methyl ethyl ketone, and diethyl ketone.

References Cited UNITED STATES PATENTS 3,025,322 3/1962 Smolin et a1260533 LORRAINE A. WEINBERGER, Primary Examiner.

L. ARNOLD THAXTON, Assistant Examiner.

1. IN A PROCESS FOR PRODUCING ACRYLIC ACID BY REACTING IN A REACTIONMEDIUM APPROXIMATELY EQUIVALENT QUANTITIES OF ACETYLENE AND CARBONMONOXIDE AT A SUFFICIENTLY ELEVATED TEMPERATURE AND PRESSURE OF FORMACRYLIC ACID, THE IMPROVEMENT COMPRISING A PRELIMINARY STEP OF FIRSTADDING ACETYLENE TO SAID REACTION MEDIUM, SAID ADDING BEING IN AN AMOUNTSUFFICIENT (1) FOR A REACTION TO TAKE PLACE AND (2) TO THEREBY REDUCEINDUCTION PERIOD AND OVER-ALL REACTION TIME, SAID REACTION MEDIUMCOMPRISING (A) A NICKEL HALIDE-COPPER HALIDE CATALYST COMBINATION, (B)WATER, AND (C) AN ORGANIC, WATER-MISCIBLE INERT SOLVENT.